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  • INSTRUMENTATION AND PHOTOGRAPHY  (2)
  • Primary production  (2)
  • 81.60J  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 54 (1992), S. 227-230 
    ISSN: 1432-0649
    Schlagwort(e): 78.65H ; 81.60J
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Poly(tetrafluoroethylene) (PTFE) does not exhibit excimer laser etching behavior at conventional, e.g., single photon absorption, emissions of 193, 248, and 308 nm, due to the lack of polymer/photon interaction. This is not surprising since the electronic transitions available to the PTFE molecule are high energy and thus require short wavelength the radiation However, by incorporating a small quantity of material into the non-absorbing fluoropolymer matrix that interacts strongly with the emitted laser energy, e.g., a dopant, successful ablation, both in terms of etch rate and structuring quality occurs. Specifically, excimer laser ablation of PTFE films containing 5, 10, and 15% polyimide (wt/wt) as a dopant was achieved at 308 nm in a fluence range of 1 to 12 J/cm2. Ablation rates for the materials increased with increasing fluence and, at the polyimide levels investigated, varied inversely with dopant concentration. All compositions exhibited excellent structuring quality.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1573-5052
    Schlagwort(e): Cyperus alopecuroides ; Hydrilla verticillata ; Ipomoea aquatica ; Primary production ; Scirpus tuberosus ; Sporobolus helvolus ; Standing crop ; Water level
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Paspalum distichum L. has been the dominant species in the monsoonal wetlands of the Keoladeo National Park in northcentral India since 1982 when grazing by water buffalo and domestic cattle was halted. Maximum water levels in these wetlands occur immediately after the end of the summer monsoon in late September of early October and then decline until the next summer monsoon the following June. After the normal 1985 monsoon, maximum water depths were around 140 cm. After the poor 1986 monsoon, maximum water depths were only around 60 cm. Paspalum distichum maximum aboveground biomass at four sites ranged from 850 g m-2 at the shallowest site to 3400 g m−2 at a deep water site. The maximum biomass of other vegetation types, which had dominated this wetland prior to 1982, ranged from 1400 g m-2 at a deep water site (Ipomoea aquatica Forsk.) to only 240 g m-2 to 400 g m-2 at a deep-water submersed site (Hydrilla verticillata (L. f.) Royle/Cyperus alopecuroides Rottb.) and at a shallow emergent site (Scirpus tuberosus Desf./Sporobolus helvolus (Trin.) Dur. et Schinz). For all vegetation types, biomass changed seasonally in response to changing water levels and temperatures. After the 1986 monsoon, above-ground biomass for all vegetation types was much lower than it had been after the 1985 monsoon. Mean below-ground biomass was very low in all vegetation types (1 to 47 g m-2). Paspalum distichum had a higher aboveground biomass at nearly all water depths in all seasons than that of the pre-1982 vegetation types. Paspalum distichum belowground biomass, however, is comparable to, or less than, that of the pre-1982 vegetation types. During years with an average monsoon, the overall primary production of these wetlands is estimated to have increased 2.5 to 3.5-fold since they were overgrown with Paspalum distichum.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Plant ecology 32 (1976), S. 87-96 
    ISSN: 1573-5052
    Schlagwort(e): Coenocline ; Drawdown ; Emergent zone ; Iowa ; Marsh ; Meadow zone ; Perturbation ; Primary production ; Simpson's index ; Submersed zone ; Wetland ; Zonation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Comparisons of a wetland coenocline before and after a drought-caused drawdown and the refilling of the basin to a higher-than-normal water level revealed that there was little difference in the above ground standing crop or in the floristic composition of the submersed, emergent or meadow zones along the coenocline. However, the position of many species along the coenocline shifted in response to these perturbations.Sagittaria latifolia, Carex spp.,Patamogeton sp. aff.pusillus all were found 2 to 4 m closer to shore.Glyceria grandis is normally found only in the meadow zone; but after the drawdown, it was found along the whole lenght of the coenocline. The drawdown also nearly eliminatedCeratophyllum demersum from the coenocline. Species richness as a result of these perturbations increased in the submersed (3.3 to 5.9) and emergent (3.6 to 4.3) zones, but decreased in the meadow zone (7.6 to 6.0). The Simpson's index in all three zones was not appreciably influenced by the perturbations. The average Simpson's indices for the meadow, emergent and submersed zones were 0.4, 0.7 and 0.5 respectively.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2019-06-28
    Beschreibung: Attention is given to the construction, calibration, and performance of a repeatable measurement system for use in conjunction with the accelerated stress testing of a-Si:H cells. A filtered diode array is utilized to approximate the spectral response of any type of solar cell in discrete portions of the spectrum. It is noted that in order to achieve the necessary degree of overall repeatability, it is necessary to pay particular attention to methods of contacting and positioning the cells.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2019-06-28
    Beschreibung: The operating principles of a new kind of room-temperature thermal radiation detector are described. In this device modulated light heats a gas, either directly or by conduction from a thin absorbing membrane, and the resultant change in density of the gas is detected by optical heterodyning. The performance of a membrane device of this kind agrees well with the predictions of theory.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Infrared Physics (ISSN 0020-0891); 23; 177-182
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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